BAGHDAD (Reuters) - Islamic State, the Sunni militant group which seeks to establish a caliphate in parts of Iraq and Syria, released a video on Tuesday that gave the strongest indication yet it might attempt to strike American targets.

The video with the theme "breaking of the American cross" boasts Islamic State will emerge victorious over "crusader" America. It follows a video posted on Monday warning of attacks on American targets if Washington struck against its fighters in Iraq and Syria.

The latest footage speaks of a holy war between the al-Qaeda offshoot and the United States, which occupied Iraq for nearly a dacade and faced stiff resistance from al Qaeda.

Islamic State's sweep through northern Iraq, bringing it close to Baghdad and in control of the second city, Mosul, drew U.S. airstrikes on the country for the first time since the end of the American occupation in 2011.

The video showed footage of President Barack Obama as well as strategic U.S. ally King Abdullah of Saudi Arabia, and attacks on American soldiers.